Concrete stairway



Sept. 25, 1962 F. LOBATO CONCRETE STAIRWAY 5 Sheets-Sheet 1 Filed Oct.17. 1958 FL ORE N T/NO LOBA T0,

INVENTOR.

HERZ/G a JESSUB BY ATTORNE Y5 Sept. 25, 1962 F. LOBATO 3,055,146

CONCRETE STAIRWAI Filed Oct. 17, 1958 5 Sheets-Sheet 4 F L OPEN TINOLOBA TO,

IN VEN TOR.

HERZ/G 8 JESS UP,

A T TORNE Y5 Sept. 25, 1962 FJLOBATO 3,055,146

' CONCRETE STAIRWAY Filed Oct. 1'7, 1958 5 Sheets-Sheet 5 FL ORENTl/VO403,410,

.15 INVENTOR.

HERZ/G a JESSUP, BY ATTORNEYS This invention relates to a concretestairway, and more particularly to new and useful improvements for ameans and method for forming a concrete stairway which comprises aplurality of step units having horizontal tread portions and integralvertical riser portions in each unit, whereby the units may be assembledto form a continuous stairway of any desired height, and havingstringers enclosing ends thereof.

An object of this invention is to prefabricate a stairway havingdiscrete step units secured in step formation to stringers prior toinstallation at place of use, each step unit having a horizontal treadportion and an integral vertical portion which can be easily handledwithout the use of large machinery to assemble the units into a stairwayof any desired height having any desired number of steps.

A further object of this invention is to provide a means and method ofassembling the step units to construct a stairway which is relativelystrong, capable of supporting great weights, and which resists settlingand cracking normally associated with concrete steps which are pouredinto conventional wooden or other molds fabricated at the location ofuse of the steps.

Another object of this invention is to prefabricate a concrete step unitof the character described which pro vides means for interlocking onestep unit with another and interlocking the assembled steps withstringers molded on location or remotely therefrom after assembly of thesteps to provide a concrete stairway of greater strength, neaterappearance and lighter weight for facilitating transporting of theassembled stairway or parts thereof to the place of use.

An additional object of this invention is to provide new and improvedmold means for prefabricating a concrete step of the characterdescribed, which is easily erected, serves as a jig for arrangingreinforcing rods in a preselected pattern for envelopment within theconcrete step unit, and which is easily disassembled for removal of theconcrete step when hardened.

A further object of this invention is to provide new and improved meansfor providing a smooth stone-free outer surface on the completedconcrete step which does not require any further treatment afterhardening to provide smooth external surfaces.

Another of the objects of this invention is to provide for adjustment ofthe mold means whereby concrete step units of varying length may bepre-fabricated.

Yet another object of this invention is to provide a new and improvedmold means for forming stringers for the stairway which is capable ofsupporting a plurality of step units in interlocking relationship forenclosure of end portions thereof within stringers cast within the moldfor locking the step units in a permanently assembled relationship, themold being adjustable to correspond to step units of varying lengths,easily dismantleab-le after solidification of the stringers for removalthereof and for repeated use of the mold, and capable of producingeither full or half stringers, as desired.

These and other objects of this invention will be more apparent from thefollowing drawings, detailed description, and appended claims.

In the drawings:

FIG. 1 is a perspective view, in elevation, of a concrete stairwaydesigned and constructed in accordance with this invention, with partsbroken away for greater clarity;

Patented Sept. 25, 1962 FIG. 2 is a fragmentary, exploded perspectiveview, illustrating the interlocking features of the individual stepunits therein;

FIG. 3 is a side view, in elevation, of a step mold means, in accordancewith this invention, for forming discrete concrete step units;

FIG. 4 is an end view thereof, as viewed from the left side of FIG. 3;

FIG. 5 is an enlarged cross-sectional view as taken on a line 55 of FIG.3, with a portion thereof in another position;

FIG. 6 is an end view, similar to FIG. 4, illustrating yet anotherposition thereof;

FIG. 7 is an enlarged perspective view, in elevation, illustrating thestep mold means in greater detail;

FIG. 8 is an enlarged perspective view, similar to "FIG. 7 illustratingthe mold means of FIG. 7 more completely assembled;

FIG. 9 is an enlarged fragmentary cross-sectional view as takensubstantially on a line 99 of FIG. 8;

FIG. 10 is a perspective view, in elevation, of a stringer mold means inaccordance with this invention, with parts broken away for greaterclarity;

FIG. 11 is a perspective view, in elevation, illustrating a portionthereof in greater detail;

FIG. 12 is an enlarged cross-sectional view taken substantially along aline 1212 of FIG. 10;

FIG. 13 is a cross-sectional view as taken substantially along a line1313 of FIG. 12;

FIG. 14 is a cross-sectional view similar to FIG. 13 illustrating aportion thereof in another position; and

FIG. 15 is an enlarged cross-sectional view taken substantially along aline 1515 of FIG. 10.

Referring to the drawings, and particularly to FIG- URES 1 and 2, thereis shown, by way of illustration but not of limitation, a stairway,generally designated by the numeral 10, of concrete construction, whichis designed and constructed in accordance with this invention. Thestairway 10 comprises a plurality of step units 11, 12 and 13, eachhaving a vertical riser portion 14 and a horizontal tread portion 16,the step units being retained in the assembled condition by a pair ofpostformed side stringer members 17 and 18.

Each concrete step unit 11-13 is, in accordance with this invention,prefabricated in a mold means to be hereinafter described, whereby thetread portion 16 and riser portion 14 thereof, are integrally formed toenclose a core or basket 19 comprising a plurality of reinforcing rodswhose selective ends extend outwardly of the step for the purpose ofinterlocking one step unit to the other and each step unit 11-13 to thestringers 17 and 18.

The cores 19' include a plurality, three in number shown in thedrawings, of L-shaped reinforcing rods 21 which are spaced within a stepunit and whose lower ends 21' depend downwardly from the vertical riserportions 14 of the unit.

A plurality of vertical openings 22, corresponding in number to theL-shaped rods 21, are provided in each horizontal tread portion 16,extending therethrough and spaced in accordance with the spacing of theL-shaped rods 21, adjacent an outer longitudinal edge 23 of the treadportions 16 and spaced inwardly therefrom. The step units 11, 12, 13 arearranged in superimposed rela tionship whereby a lower edge surface 24of a riser portion 14 rests on the upper outer surface of the treadportion 16 and adjacent the edge 23 thereof, with the outwardlyextending ends 21' of each rod 21 residing within the openings 22 tointerlock one step unit with the other, the ends 21 of the lowermostunit, 13 in FIG. 1, being enveloped within a foundation (not shown) ifdesired, or optionally cut off.

in its length alone. means 41 which may conveniently comprise a bench orThe cores 19 further include spaced elongated longitudinal reinforcingrods 26 having ends 26' extending outwardly of the step unit. Selectiveends 26' are preferably tied together as by elongated tie rods 27, as bywelding or the like, after which the stringers 17 and 18 are moldedwithin a stringer mold 20 (FIGURES -14) to unit 11-13, the risers 14 andtreads 16 are preferably provided with thickened portions of fillets 29at the intersection of the inner surfaces thereof.

It is to be understood that although a substantially fiat riser portion14 and tread portion 16 is herein described and having merely a slightlyrounded outer corner 31, steps of any desired configuration may beformed such as having a rounded head or leading ledge indicated indotted lines 31' of step unit 11 in FIG. 2, or a squared overhang,indicated in dotted lines 31" of step unit 12, in the same figure, ifdesired.

An important feature of this invention is the provision of improvedapparatus or mold means for precisely, accurately and quicklyprefabricating step units like units 11-13 which can be readilyassembled in interlocking relationship and permanently secured in suchrelationship by stringers molded thereto, the entire assembly beingreadily transportable for installation at the location of use. The stepunits may be optionally assembled at the illustrated, the means 40 beingillustrated as adapted for use in forming two step units, like units11-13, at a time.

-It is to be understood, however, that any number of units may beprefabricated by merely modifying the means 46 The means 41 includes asupport .table 42 supported as by legs 43-, to pivotally support a frame44 as by stub shafts or pins 46 thereof rotatably disposed in bearings47 mounted on the frame 44.

The frame 44 includes a horizontal bed 48 for supporting elongate baseplate 52 common to a plurality of mold means 53, two of them beingillustrated in FIG. 3.

The base plate 52 is preferably L-shaped in configuration, having arelatively flat longitudinal portion 54, on which the tread portion 16is formed, substantially perpendicular to a second relatively flatlongitudinal portion 56, on which the riser 14 is formed, the portions54 and 56 meeting at an intermediate portion 57 which is angularlydisposed relatively to both portions 54 and 56. The portion 54 serves toform the inner surface of the horizontal tread portion 16 of a stepunit, the portion 56 serves to form the inner surface of the verticalriser portion 14 of the step unit, while the intermediate portion 57serves to form the inner surface of the fillet 29 of the step unit. Thebase plate 52 is preferably for-med of sheet metal or the like andreinforced as by L-shaped angle pieces 58, corresponding inconfiguration to the portions 54, 56 and 57.

As best seen in FIGS. 4 and 6, a pair of side wall members 62 and 63 areremovably disposed on the base plate 52. Each side wall 62, 63 ispreferably of angular crosssection and L-shaped in configuration toconform sub- :stantially to the configuration of the base plate 52,having secured at each end thereof, as by welding or the like, endplates 64 having threaded apertures 66 therethrough. A gusset 67 isprovided on each side wall 62, 63 to conform to the beveled or angularsurface 57 of the base plate 52 whereby the lower surfaces 68 of eachside wall 62, 63 together with the outer edge surface 69 of each gusset67, conforms to the configuration of the base plate 52.

Removably secured to the end plates 64 of the side walls 62, 63 andspanning the walls 62 and 63 is a pair of end walls 71 and '72. The endwalls 71 and 72 may be conveniently formed of angular cross-section, theupstanding leg of each being substantially equal in width to theupstanding legs of the sidewalls 62 and 63. The end walls 71 and 72 areprovided with apertures therethrough whereby fastening members 73 mayextend therethrough and threadedly engage the threaded apertures 66 ofthe end plates 64 for removably securing the walls 71 and 72 to the sideWalls 62 and 63, lower edges 74 thereof being in contact with the baseplate 52. To complete the mold means 53, thereby forming a cavity 76, acover member or outer wall 77 is removably secured to the base plate 52.The cover member 77 may be formed of sheet metal or the like, inL-shaped configuration, conforming to the outer edges 78 of the walls 62and 63 and the outer edges 79 of the end walls 71 and 72. The covermember 77 may be rounded at its corner 81 and provided with reinforcingmembers 82 and 83, welded or otherwise secured to the outer longitudinaledges 84 and 86, respectively, thereof.

The side walls 62 and 63 are secured to the base plate 52 by a pluralityof bolts 87 (see FIG. 8) extending through an aperture 88 of the baseplate 52, and aligned apertures 89 of the side wall members 62 and 63and threadedly secured by nuts 91.

To adapt the base plate 52 for greater versatility, additionalapertures, like 88 and indicated at 92 and 92', are provided in the baseplate 52 whereby the side walls 62 and 63 may be shifted longitudinally,relative to the base plate 52, to space them closer together or fartherapart, as desired, to form step units of varying lengths. The apertures88, 92 and 92' are preferably countersunk, as illustrated in FIG. 8,whereby an aperture, such as 92', extending within the cavity 76 of themold means 53 when a step of a length lesser than maximum is beingformed, can be covered as by a countersunk head of a bolt 93 to avoidleakage of cementitious material when poured into the cavity 76. In theevent that the apertures 92 or 92 are used to make a form of a differentlongitudinal dimension, end members 71 and 72 and cover 77, ofappropriate dimension, may be substituted for the ones illustrated tocompensate for the differing dimensions, or optionally, a cover and endmembers of maximum length may be provided each having a plurality oflongitudinally spaced apertures suitably plugged when not used. A nut91' is preferably secured as by welding or the like to the undersurfaceof the cover means 77 and an elongated bolt 87' indicated in brokenlines substituted for the bolt 87 to secure the cover '77 to the baseplate 52 when a maximum length is used.

The mold means 53 is secured in covered position by providing clamps 94having outer ends 96 engaging the reinforcing strip 83 of the covermember 77 and a reinforcing strip 97 secured to the undersurface of thebase plate 52 to grip the strips and insure a non-leaking engagementbetween the cover member 77, side walls 62, 63, end wall 71 and baseplate 52. The mold means 53 is additionally secured by bolts or pins 104extending therethrough as will be hereinafter described.

In order to accurately and precisely space and support the reinforcingrods 21 and 26 of the basket 19 previously described, a plurality ofspaced apertures 98 are provided in the end wall 71 extendingtherethrough. The L-shaped rods 21 are automatically and accuratelyspaced by the apertures 98 and supported in the spaced relationship.Similar apertures 99 are provided in the side walls 62 and 63, extendingtherethrough, for spacing and supporting the longitudinal elongatedreinforcing rods 26, the bars 21 and 26 having their ends 21 and 26'respectively extending outwardly of the cavity 76. The

rods 21 and 26 are loosely supported as by means of the apertures 98 and99, and secured together as by welding or the like at points at whichthey intersect, as indicated at 101. Additional L-shaped rods 21a arepreferably provided equally spaced between the rods 21 and welded orotherwise secured to the rods 26 to provide further reinforcement, buthaving their outer ends terminating within the cavity 76.

In order to form the vertical openings 22 extending through the treadportions 16 of the step units 11-13, aligned apertures 111-2 and 1133are provided in the top member 77 and base plate 52 respectively,through which bolts or pins 164 are inserted, after the cover 77 hasbeen positioned over the side and end walls. The shank of each pin 104extends through the cavity 76 to form the openings 22 in the treadportion 16 of the step unit when the cementitious material is pouredinto the cavity 76. An additional longitudinal reinforcing rod 166 ispreferably secured, by welding or the like, to the L- shaped reinforcingrods 21 to provide additional reinforcement between the opening 22 andthe outer edge 23 of the tread members 16. The rod 1% does notnecessarily extend through the side walls 62 and 63 and may terminateadjacent thereto.

For convenience, the base plate 52 rests on the bed plate 48 in aposition convenient for installation of the side and end walls and therods 21 and 26, such as shown in FIG. 4, after which the cover member 77is secured in place, as previously described, after which the end wallmember 72 is removed by removing the fastening means 73 therefrom.

The base plate 52 is then rotated into a tilted position illustrated inFIG. 5, wherein cementitious material may be poured, as through theopening 72' formed at what is now the upper end of the mold means 53 tofill the now lower portion of the cavity 76 to a level approximated bythe line 167, after which the mold is rotated to the positionillustrated in FIG. 6 to fill the upper portion of the cavity 76 to alevel flush with the outer surfaces of the upper end plates 64 of theside walls 62, 63. Stops 168, of angular form, are preferably securedadjacent a rear edge of the bed plate 48 against which the base plate'52 may abut while being supported at a tilted angle by a removablewedge 168' for the pouring position of FIG. 5. Cables 1139, or otherties, indicated in broken lines, in FIG 6, may be provided to assist insupporting the mold 53 in various positions.

The end member 72 may then be replaced and locked' in place by thefastening means 73 to prevent outflow of the cementitious material.

The base plate 52 i preferably vibrated or oscillated during pouring inthe positions of FIGS. 5 and 6 in a manner to be hereinafter describedto cause the aggregate within the cementitious material to redistributeand thereby cause the finer material thereof to rise against the plate77, providing smooth and stone-free outer surfaces which do not requirefurther finishing after hardening. Vibration or oscillation alsoprovides a means for removing air bubbles that normally form duringpouring of the material. Such air bubbles are eliminated while the moldmeans and base plate 52 are vibrated during pouring. After the cavity 76is completely filled the end Wall 72 is replaced as previously describedand the mold means 53 is stored in the position indicated in PEG. 6 todry and harden. After the step unit has hardened for approximately 40hours the cover 77 may be removed; the side walls 62 and 63 and endwalls 71, 72 may be removed from the base plate 52 to free the step unitafter it has completely dried.

The base plate 52 is preferably lifted and removed from the bedplate 48for drying in order that the bedplate may be continually used to formadditional step units by placing another base plate 52 and componentparts of molds like 53 thereon.

Vibrating means, indicated generally by the numeral 110 (see FIGS. 3 and4), may be one of various types.

The vibrating means as herein illustrated, comprises an eccentric collar111 secured as by a flexible cable 112 to the bed plate 48 of the frame44. The collar 111 is rotated as by a shaft 113 secured to a pulley 114driven by a pulley belt 116 and a motor-driven pulley 117, driven by amotor 118 mounted on the support means 41. The flexible cable 112 isattached as at 119 to a depending extension 121 of the bed plate 48which, after being pulled downwardly at one edge thereof by theeccentric bushing 111, is returned by a spring 122 secured as to theopposite edge thereof. It is to be understood, however, that variousvibrating means may be employed to provide an oscillatory motion to thebase plate 52, thereby causing a vibration of the mold means 53 and thecementitious material therein to rearrange the particles of aggregationwithin the cementitious material to bring the finer particles thereof tothe surface, that is, against the cover member 77 to provide stone-free,bubble-free exterior surfaces on the finished step unit.

In order to complete the stairway 10- by enclosing step units such as11-13 within the stringers 17 and 18, the stringer mold means 20 isprovided wherein the step units 1113 are pre-assembled, i.e., arearranged in stepped formation with the depending rod end portions 21 ofone step uni-t engaging and residing within openings 22 of an adjacentstep unit within the stringer mold means 20 after which stringers 17, 18are cast adjacent the sides of the steps to enclose the ends of the stepunits and outwardly extending ends 26' of the reinforcing members 26 andthe diagonal tie rods 27 therein.

Referring more particularly to FIGS. 10-15, an apparatus for formingstringers to complete the stairway is illustrated 'wherein the stringermold means 20 comprises a frame, generally designated by the numeral125, on which a pair of stringer molds 12s and 127 are removably securedforming a pair of spaced cavities 12S and 129, respectively, for formingthe stringers 17 and 18, respectively.

The frame comprises a pair of spaced channel members 131 having theiropen sides facing each other and being adjustably secured to each otheras by a pair of cross-braces 132 pivot'ally secured at their upper ends133 to a lower wall of each channel member 131 and adjustably secured attheir lower ends 134 as by fastening means 136 extending throughapertures of the lower ends 134 and elongated slots 137 of the lowerwall of the channel members. The members 131 are additionally secured bya transverse telescoping brace 138. The brace 138 preferably includes aset screw 139 to lock the channel members 131 in a predetermined spacedposition. The frame 125 is supported in an inclined position by a pairof telescoping leg members 141 pivotally secured to the undersurface ofeach channel member 131 adjacent their elevated ends and braced as bytelescoping brace members 142 having ends pivotally secured to the legs141 and the channel members 131, whereby a desired angle of inclinationof the frame 125 may be achieved by adjusting the overall length of thelegs 141 and braces 142 after which the legs 141 and braces 142 may belocked as by set screws 143 and 144-, respectively, to retain suchangular position.

Each stringer mold 126 and 127', of the stringer mold means 211,comprises an inner wall 146, formed of discrete upper and lower innerwall members 147 and 148, respectively, a lower wall 149, an outer wall154), an upper wall 151, and end walls 152 and 153. The inner -wall 146,the lower wall 149, and the outer wall 150 of each stringer mold 126,127, are identical with the exception that the walls of one stringermold are mirror images of the walls of the other stringer mold and aretherefore designated by like numbers with the exception of primednumbers being used to designate corresponding parts in the mold 127. Theend walls 152 and 153 are common to both molds 126, 127, while the upperwalls 151 are interchangeable.

Each of the lower inner wall members 148, 148' comprises a plurality ofsubstantially triangular vertical walls 152 removably secured to theouter walls 153 of the channel members 131 as by a' bolt or screwfastener 154. Each vertical wall 152 is provided with an integrallyformed inwardly extending flange 156, each flange including a horizontalportion, a vertical portion and an intermediate angular portioncomplementary to the undersurface of the step units like 11-13 tosupport these step units in assembled stacked relationship, one beingindicated in FIG. and three step units 11, 12 and 13 illustrated in FIG.12. The triangular walls 152 and their integral flanges 156 thereby forma stepped configuration when attached to the channel members 131complementary to the stepped configuration of the undersurface of thestep units 11-13 When assembled.

The upper inner walls 146, 146', are adapted to conform to the uppersurface of the stepped configuration of the step units when assembledand include vertical walls 157 of substantially triangularconfiguration, each wall 157 having an inwardly extending integralflange 158 complementary to the outer surface of the riser and the treadportions of the step units 11-13. The members 157 are secured in stepconfiguration to a longitudinal member 159, 159', of the molds 126, 127,respectively, as by sandwiching an upper edge 157 thereof betweenangular elements of the members 159, 159 and secured against innermovement by a fastening member 161 comprising an elongated rod havingone end 162 abutting the flange 158. The rod 161 is threaded at itsouter end 163 which extends through an aperture of the longitudinalmembers 159, 159', and is in engagement with a nut 164 thereon. Thelongitudinal members 159, 159, are each preferably provided with anupturned flange 166 to which an elongated angular piece 167 is securedfor securement to a transverse clamp 168, to be hereinafter described,whereby the longitudinal members 159, 159', and thereby the discretemembers 157, are securely held in place, with the flanges 158 inabutment with the assembled step units 11-13.

Each of the bottom walls 149 includes an upwardly extending flange 169for removably securing the wall to its adjacent channel member 131 as bythe fasteners 154. The wall 149' is preferably centrally split andjoined as by a longitudinal hinge 171 to facilitate parting of the moldfrom the stringer when the stringer has hardened. In practice, it hasbeen found advantageous to form a portion of the lower wall 14-9 as byan inturned flange 172 integral with an outer wall 150, 151i and securedas by welding or the like to the hinges 171, whereby an outer wall 151150 and its integral flange 172 may be pivoted outwardly at the hinge171 to part the Walls 150172, tl' 172, away from its stringer whenhardened.

The outer walls 150, 153" are provided at their upper edges with anelongated angular member 173, or with optionally formed outwardly facingintegral flanges, to engage hooked ends 174 of the transverse clampmembers 168, there being a hooked member 174 at each end of the clamps168 to engage each angular member 173 of both outer walls 150, 150', asbest seen in FIGS. 10 and 13. The clamps 168 may be secured to the wallmembers 150, 150 as by set screws 176. The clamps 168, spanning theentire width of the mold means 23, provide convenient securenrent forthe upper inner walls 146, 146' as by fasteners, in the form. of boltsand nuts 177.

Each upper wall 151 is preferably formed of a pair of elongated sheetmetal members 178 abutting at adjacent edges and secured together as bya hinge 179. Each elongated member 178 is preferably curved downwardlyat its edges 181 to provide a curved edge on the finished stringers 17,18. The upper wall 151 may be removably secured as by a hooked clamp 182 engaging the angular strip 173 of the outer walls 159, at one end 183thereof and to the upper wall 151 at the other end thereof as by clips134 whereby the wall 151 may be easily and quickly removed from theupper edge of the stringer when the stringer has hardened, the hinge 171facilitating disengagement of the curved edges 181 from the stringer.

The end walls 152 and 153 are preferably of sufficient length to spanthe entire width of the mold means 20, in its maximum expandedcondition, and are secured at each end thereof to the outer walls 150,150' by suitable fasteners such as nuts and bolts 186 indicated in. FIG.10. Additional longitudinally spaced apertures 187 are preferablyprovided in the end walls 152 and 153 for the securement of the endwalls 152, 153 to the outer walls 150, 150 in various adjustedpositions, the apertures 187 eing plugged temporarily when not used bycountersunk screws like 93 described in relation to the step mold meansof FIG. 9.

'It will therefore be clearly understood from the foregoing descriptionthat upper and lower inner wall members 147 and 148, respectively,having sandwiched between their flanges 15S and 156, respectively, theouter ends of the step units 11-13, together with a lower wall 149, anouter Wall 150, an upper wall 151, and the end walls 152, 153, common toboth stringer molds 126 and 127, form discrete cavities 128, 129 forreception therein of cementitious material in plastic form whereby theoutwardly extending ends 26" of the longitudinal reinforcing members 26and a diagonal reinforcing member 27 secured thereto, extend into thecavities 128, 129 and are imbedded in the cementitious material of thestringer to securely join the step member 11-13 together when thestringer has hardened.

The channel members 131 are preferably so spaced, as by means previouslydescribed, to position the outer edges 186 of each step unit 11-13inwardly of the cavities 128, 129 whereby the edges 186 are enclosed bythe cementitious material poured therein to further strengthen thestairway 10. If desired, additional reinforcing rods such as indicatedat 187 in FIGS. 13 and 14 may be spaced within the cavities 128, 129 toreinforce the stringers 17, 18, respectively.

To remove a finished stairway 10, the clamps 168 are disengaged andremoved to unfasten the walls 150, 150' and longitudinal members 159,159 whereby the longitudinal members and their attached upper innerwalls 147, 147' may be easily removed therefrom. The top wall 151 may beeasily removed because of its hinged construction, and the outer wall151) and lower wall portion 172 broken away from the finished stringerby pivoting the Walls at the hinge 171. The set screw 139 and fasteningmeans 136 may then be loosened to draw the channel members 131 inwardlyto break away the lower wall 149 and the lower inner walls 148, 1 58from the inner surface of the stringer to free the step units and theirnow integral stringers from the mold 20, whereby the mold may be removedfor subsequent use to form other stairways like 10.

To facilitate filling of the cavities 128, 129, an opening 188, ofcircular or other configuration, is formed in each of the vertical walls157 of the upper inner walls 146, 146 thereby affording access to thecavity. The openings 188 may be closed as by a closure member 189 havinga body 191'? conforming to the configuration of the opening 188, securedby welding or the like to a transverse rod 191 engageable with clips 192secured to the vertical wall 157 whereby the opening 188 may be closedafter pouring cementitious material into the area of the cavities 128,129 below the opening, after which material may be poured through anopening 188 of a vertical wall 157 thereabove.

It will be therefore clearly understood from the foregoing descriptionthat stringers, like 17, 18 may be formed on each side of the stairwayto securely fasten step units thereof together in a manner in whichtriangular-shaped webs 190 are formed (see FIG. 1) having uppercoextensive surfaces 191 to form a full stringer.

-In some instances it is preferred to form what is known in the art as ahalf-stringer, that is, where the upper surface thereof conformssubstantially to the stepped upper surfaces of the step units. For thispurpose, as best seen in FIG. 14, an additional aperture may be providedin the clamp 168 whereby the longitudinal members 159, 159' may beshifted outwardly to a position shown in FIG. 14, wherein a verticalwall 157 is shifted outwardly to abut its outer Wall 150, 151 in theposition shown in this figure, whereby the integral flange 158 of eachwall 157 overlies the cavity 129 of reduced area to form the upper wallthereof, in which instance the upper wall 151 previously described isunnecessary. The upper inner walls 146, 146 are secured to the clamps168 as by the fasteners 177 extending through the additionally providedapertures in the clamp 168 to secure the upper inner wall means 146, 146in the abutting position described, the resultant half-stringer beingindicated by a broken line 18 in FIG. 1.

In order to provide access to the cavity 129' that is formed, an opening192, of rectangular or other configuration, is provided in thehorizontal portion of the fianges 158 and communicating with the cavity129' for pouring of cementitious material therethrough, the opening 192being closa-ble as by a closure means 193, similar to the closure means189 and comprising abody 194 conforming in configuration to the opening192 and having a rod 196 secured thereto by welding or the like andengageable with clips 197 mounted on the horizontal portion of theflange 158.

While I have herein shown and described my invention in what I haveconceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of myinvention, which is not to be limited to the details disclosed hereinbut is to be accorded the full scope of the claims so as to embrace anyand all equivalent devices and methods.

What I claim as new and desire to secure by Letters Patent is:

1. A concrete stairway comprising: a plurality of L- shaped step unitsjuxtaposed in stepped relationship, each of said units having ahorizontal tread portion and a vertical riser portion integral therewithhaving a plurality of spaced vertical openings therethrough adjacent anouter edge thereof; a plurality of L-shaped rod members extendingthrough said tread and riser portions and having outer ends extendingoutwardly from said riser portion, said outer ends of the L-shapedmembers of one step unit residing in said openings of an adjacent stepunit, said riser portion of one step unit resting on said tread portionof an adjacent step unit adjacent said outer edge; a plurality of spacedelongated longitudinal rod members extending through said tread andriser portions transversely of said L-shaped rod members and havingouter ends extending outwardly of said step unit; a pair of stringermeans of concretious material having flat surfaces juxtaposed fiushagainst the ends of said step units, one on each side thereof, andhaving said outer ends of said longitudinal rod members embeddedtherein, a plurality of diagonal elongate rod members secured toselected ends of said longitudinal rod members of each step unit, andsaid diagonal members being spaced outwardly of said step units andbeing embedded in said stringer means.

2. A concrete stairway comprising: a plurality of L- shaped step units,each unit having a horizontal tread portion and an integral verticalriser portion, each of said tread and riser portions having an outeredge; a plurality of spaced L-shaped reinforcing rod members extendingthrough said step units transversely of said edges and having ends, oneof said ends of each member terminating in said tread portion and spacedinwardly of said edge thereof, the other of said ends extendingoutwardly of said riser portion edge; a plurality of spaced longitudinalreinforcing rod members extending through said tread and riser portionsand having ends extending outwardly thereforrn; and a plurality oflongitudinally spaced apertures corresponding in number to said L-shapedreinforcing rod members, spaced inwardly from said tread edge, theoutwardly extending ends of the L-shaped reinforcing members of one ofsaid step units residing in said apertures of an adjacent step unit andsaid outer riser edge of each of said units being in abutment with thetread portion and adjacent said edge thereof of an adjacent step unit;molded stringer means having flat surfaces adjacent the ends of saidstep units and having said ends of said longitudinal reinforcing rodmembers embedded therein to hold the step units and stringers inassembled relationship, said L-shaped reinforcing rod members beingsecured to said longitudinal reinforcing rod members, and diagonalreinforcing rod members secured to selected outwardly extending ends ofsaid longitudinal reinforcing members, said diagonal reinforcing meansbeing embedded in said stringer means.

References Cited in the file of this patent UNITED STATES PATENTS863,760 Schachner Aug. 20, 1907 875,113 Schachner Dec. 31, 19071,304,533 Bois May 27, 1919 1,533,166 Daly Apr. 14, 1925 2,154,937Henderson Apr. 18, 1939' 2,239,428 Miohaud et a1 Apr. 22, 1941 2,289,439Kogl July 14, 1942 2,330,148 Rogge Sept. 21, 1943 2,520,452 Brune Aug.29, 1950 2,558,615 Johnson June 26, 1951 2,652,614 Como Sept. 22, 1953FOREIGN PATENTS 1,163,784 France Sept. 30, 1958

